Consumable cartridge for a plasma arc cutting system

ABSTRACT

A frame for a replaceable, unitary consumables cartridge configured for installation into a plasma arc torch. The frame includes a hollow body adapted to receive a translatable contact start electrode. The body has an internal surface and an external surface and includes: a substantially cylindrical metallic core; an electrically insulative overmolded plastic casing at least substantially surrounding a circumference of a distal end of the substantially cylindrical metallic core; and a set of flow passages fluidly connecting the external surface of the hollow body and the internal surface of the hollow body, the flow passages offset to impart a swirling fluid flow pattern to a plasma gases passing therethrough.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional of U.S. Ser. No. 62/756,996, filedNov. 7, 2018 and entitled “Plasma Torch Cartridge.” This application isa continuation-in-part of U.S. Ser. No. 15/971,703, filed May 4, 2018and entitled “Consumable Cartridge for a Plasma Arc Cutting System,”which is a continuation of U.S. Ser. No. 14/708,957, filed May 11, 2015,which is a continuation-in-part of U.S. Ser. No. 14/079,163, filed Nov.13, 2013 and entitled “Automated Cartridge Detection for a Plasma ArcCutting System.” application Ser. No. 14/708,957 is also anonprovisional of U.S. Ser. No. 61/991,114, filed May 9, 2014 andentitled “Cartridge Type Consumable Assembly for a Plasma Arc CuttingSystem,” and is also a nonprovisional of U.S. Ser. No. 62/036,393, filedAug. 12, 2014 and entitled “Cost Effective Cartridge for a Plasma ArcTorch.” application Ser. No. 14/708,957 is also a continuation-in-partof International Patent Application No. PCT/US14/56546, filed Sep. 19,2014 and entitled “Thread Connection for a Torch System.” Thisapplication is continuation-in-part of application Ser. No. 15/971,703which is a continuation of U.S. Ser. No. 14/708,972, filed May 11, 2015and entitled “Consumable Cartridge for a Plasma Arc Cutting System,”which is a continuation of U.S. Ser. No. 14/708,957, filed Aug. 12,2015, which is a continuation-in-part of U.S. Ser. No. 14/824,946, filedNov. 13, 2013 and entitled “Cost Effective Cartridge for a Plasma ArcTorch.” The contents of all of these applications are herebyincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention relates generally to the field of plasma arc cuttingsystems and processes. More specifically, the invention relates tomethods and apparatuses for simplifying, optimizing and decreasing thetime and cost of cutting through the use of improved consumablecartridges.

BACKGROUND

Plasma arc torches are widely used in the cutting and marking ofmaterials. A plasma torch generally includes an arc emitter (e.g., anelectrode), an arc constrictor or constricting member (e.g., a nozzle)having a central exit orifice mounted within a torch body, electricalconnections, passages for cooling, and passages for arc control fluids(e.g., plasma gas). The torch produces a constricted ionized jet of agas with high temperature and high momentum. Gases used in the torch canbe non-reactive (e.g., argon or nitrogen) or reactive (e.g., oxygen orair). During operation, a pilot arc is first generated between the arcemitter (cathode) and the arc constrictor (anode). Generation of thepilot arc can be by means of a high frequency, high voltage signalcoupled to a DC power supply and the torch or by means of any of avariety of contact starting methods.

Known consumables suffer from a host of drawbacks both before and duringa cutting operation. Before a cutting operation, selecting andinstalling the correct set of consumables for a particular cutting taskcan be burdensome and time-consuming. During operation, currentconsumables encounter performance issues such as failing to effectivelydissipate and conduct heat away from the torch and failing to maintainproper consumable alignment and spacing. Furthermore, currentconsumables include substantial amounts of expensive materials, such asCopper and/or Vespel™, which leads to significant manufacturing costsand inhibits their widespread commercialization, production andadoption. What is needed is a new and improved consumable platform thatdecreases manufacturing costs, increases system performance (e.g., heatconduction, component alignment, cut quality, consumable life,variability/versatility, etc.) and eases installation and use ofconsumables by end users.

SUMMARY OF THE INVENTION

The present invention provides one or more cost effective cartridgedesigns that reduce manufacturing costs, facilitate cartridgecommercialization and production, improve installation and ease of useby end users, and increase system performance. In some embodiments,numerous traditional consumable components (e.g., swirl ring, nozzle,shield, retaining cap, and electrode components) are redesigned. In someembodiments new components (e.g., an electrode sleeve, a lock ring,and/or an interfacing insulator) are created. In some embodiments, aconventional swirl ring is replaced with a different feature within thetorch body that imparts a swirl to a gas flow within the torch body(e.g., a swirl feature having flow holes built directly into a body ofthe nozzle). In some embodiments, a nozzle shield is electricallyisolated from the nozzle (e.g., by using anodized aluminum and/orplastic).

In some embodiments, each cartridge comprises one or more of thefollowing consumable components: a frame or body having one or moresections; an arc emitter (e.g., an electrode); an arc constrictor or arcconstricting member (e.g., a nozzle); a feature to impart a swirl to agas within the plasma torch (e.g., a swirl feature built into thenozzle, a swirl ring, or another swirl feature); a shield (e.g., anozzle shield that is electrically isolated by the use of aluminum,anodized aluminum and/or a plastic material); an emitting element (e.g.,a hafnium emitter); and/or an end cap. In some embodiments, a cartridgeincludes a substantially copper portion (e.g., a copper inner core) anda substantially non-copper portion (e.g., a non-copper portion externalto the inner core). In some embodiments, a cartridge can be used on ahandheld plasma cutting system and/or a mechanized plasma cuttingsystem.

In some embodiments, a cartridge has a resilient element, such as aspring electrode or a spring start mechanism affixed to an electrode,integrated directly into the cartridge and designed not to be separableor disassemblable from the cartridge. The resilient element can be inphysical communication with the frame and/or can be configured to pass apilot current from the frame to the arc emitter. The resilient elementcan bias the arc emitter in a direction along an axis of the resilientelement, e.g., by imparting a separating force. In some embodiments, theseparating force has a magnitude that is less than a magnitude of acoupling force holding the cartridge together.

In some embodiments, the cartridge has enhanced cooling and insulativecapabilities, reduced manufacturing and material costs, and/or improvedrecyclability, durability and performance. In some embodiments, thecartridge provides consumable components in one integrated piece. Insome embodiments, the cartridge enables a significantly reduced torchinstallation time (e.g., by a factor of 5-10); ensures that mating partsare always chosen correctly for a given cutting task; improves heatdissipation and/or conduction capabilities; enables easier recognitionof appropriate consumable components for a given cutting task; enhancesconsumable alignment and/or spacing; and/or reduces operator error. Insome embodiments, heat is moved substantially away from the torch, butnot so far as to heat or melt plastic components. In some embodiments,using a metal besides copper (e.g., in a region outside an inner core ofcopper components) helps move heat away from the torch. In someembodiments, the cartridge allows specific combinations of consumablesto be pre-chosen for specific cutting tasks.

In some embodiments, the cartridge frame includes a strongly thermallyconductive material, e.g., aluminum, copper, or another highlyconductive metal. In some embodiments, the cartridge frame is formed bymolding. In some embodiments, at least one of the first end of thecartridge frame or the second end of the frame includes a threadedregion shaped to engage a complementary component. In some embodiments,the shield, the arc constrictor and the frame are thermally coupled. Insome embodiments, an external surface of the frame is shaped to connectto a retaining cap. In some embodiments, the cartridge includes a shieldinsulator connected to the frame. In some embodiments, the shieldinsulator is press fit to the frame.

In some embodiments, a cartridge cap defines an aperture of the arcemitter and includes a fluid sealing surface disposed about acircumference of the arc emitter aperture. In some embodiments, theelectrode comprises a spring. In some embodiments, the cartridge capextends within a base region of the arc constricting member to alocation near the set of swirl holes. In some embodiments, a base of thearc constricting member is formed by molding. In some embodiments, aretaining cap is connected to the cartridge body. In some embodiments,the retaining cap comprises a plastic. In some embodiments, the arcconstricting member and the electrode are connected to the retaining capvia a base of the arc constricting member.

In some embodiments, a cartridge includes a shield connected to thecartridge body. In some embodiments, the shield is connected to thecartridge body via a shield insulator. In some embodiments, the shieldinsulator is press fit to at least one of the shield or a base of thearc constricting member. In some embodiments, the shield insulator iselectrically insulative. In some embodiments, the shield insulator isthermally conductive. In some embodiments, the shield insulator includesanodized aluminum. In some embodiments, a sleeve is disposed about aportion of the electrode. In some embodiments, the sleeve includes ananodized layer formed to electrically isolate the electrode from a baseof the arc constricting member. In some embodiments, the sleeve includesa set of flow surfaces configured to facilitate fluid flow within theplasma torch, e.g., to improve cooling.

In some embodiments, a cartridge (or consumable assembly) includes aseal disposed within the cap insert. In some embodiments, a cartridgeincludes a retaining cap directly connected to the gas flow diverter. Insome embodiments, the retaining cap is formed of a plastic. In someembodiments, the arc constrictor and the emissive member are connectedto the retaining cap via a swirl ring. In some embodiments, the shieldinsulator is press fit to at least one of the shield and the gas flowdiverter. In some embodiments, the shield insulator is electricallyinsulative. In some embodiments, the shield insulator is thermallyconductive. In some embodiments, the shield insulator includes anodizedaluminum. In some embodiments, the shield has a heat capacity to currentratio of about 2 to about 4 W/m-° K-A. In some embodiments, thecartridge or consumable assembly includes a sleeve disposed about aportion of the emissive member. In some embodiments, the sleeve includesan anodized layer formed to electrically isolate the emissive memberfrom a base of the arc constrictor. In some embodiments, the sleeveincludes a set of flow surfaces.

In some embodiments, the cartridge is replaced as a unit. In someembodiments, a length of the emitting element can be adjusted to matchthe life of the nozzle, such that the cartridge parts reach the end oftheir useful lives at approximately the same time. In some embodiments,cut quality can be similar to that achieved using current consumables.In some embodiments, a cartridge type consumable assembly including aspring electrode disposed within a nozzle body and a sealing devicedisposed within a lock ring. The sealing device can be configured toconnect to a plasma arc torch. The spring electrode can include athumbtack or contact element that extends within the electrode body andis connected to a spring disposed between the contact element and theelectrode body. In some embodiments, the electrode sleeves can haveshaped (e.g., scooped) front ends to direct gas flow within thecartridge.

In one aspect, the invention features a replaceable cartridge for aplasma arc torch. The replaceable cartridge includes a cartridge bodyhaving a first section and a second section. The first and secondsections are joined at an interface to form a substantially hollowchamber. The interface provides a coupling force that secures the firstand second sections together. The cartridge also includes an arcconstricting member located in the second section. The cartridge alsoincludes an electrode included within the substantially hollow chamber.The cartridge also includes a contact start spring element affixed tothe electrode. The spring element imparts a separating force that biasesthe electrode toward at least one of the first section or the secondsection of the body. The separating force has a magnitude that is lessthan a magnitude of the coupling force.

In some embodiments, a gas input moves the electrode and overcomes theseparating force. In some embodiments, at least a portion of theelectrode and the contact start spring element are irremovably disposedwithin the substantially hollow chamber. In some embodiments, a base ofthe arc constricting member is anodized. In some embodiments, thecartridge has a region with a thermal conductivity of between about200-400 Watts per meter per degree Kelvin. In some embodiments, theshield has a heat capacity to current ratio of 2-4 W/m-° K-A. In someembodiments, the cartridge includes a cap insert connected to the secondsection of the cartridge body, the cap insert substantially orientingthe electrode and retaining the electrode within the cartridge body.

In another aspect, the invention features a sealed cartridge unit for aplasma arc torch. The cartridge unit includes a substantially hollowframe including a first substantially hollow portion defining a firstend and a second substantially hollow portion defining a second end. Thecartridge unit includes an arc emitter located within the frame. The arcemitter is translatable relative to the frame. The cartridge includes anarc constrictor attached to the second end of the frame. The cartridgeincludes a resilient element in physical communication with the frame.The resilient element biases the arc emitter toward one of the first endor the second end to facilitate ignition at or near the arc emitter.

In some embodiments, a gas input moves the electrode and overcomes theseparating force. In some embodiments, the frame includes an electricalinsulator. In some embodiments, the frame includes at least one of ametal or a strongly thermally conductive material. In some embodiments,the frame is anodized. In some embodiments, the cartridge includes atleast one set of flow holes, each flow hole in the set of flow holesradially offset from the other flow holes. In some embodiments, the flowholes have a total cross-sectional area of about one square inch. Insome embodiments, the first end is configured to connect to a shield viaa shield insulator, and the shield, the arc constrictor and the frameare thermally coupled. In some embodiments, the cartridge unit has aregion with a thermal conductivity of between about 200-400 Watts permeter per degree Kelvin. In some embodiments, the cartridge includes acartridge cap disposed in the second end of the frame, the cartridge capshaped to contact the arc emitter and to retain the arc emitter withinthe frame.

In another aspect, the invention features a replaceable, unitaryconsumable assembly for a plasma arc torch. The consumable assemblyincludes a gas flow diverter, an arc constrictor in physicalcommunication with the gas flow diverter, an emissive member disposedsubstantially within the gas flow diverter and the arc constrictor, anda resilient arc initiator disposed between the emissive member and atleast one of the gas flow diverter or the arc constrictor. At least aportion of each of the gas flow diverter, the arc constrictor, theemissive member and the arc initiator are irremovably integrated withinthe consumable assembly.

In some embodiments, the emissive member includes an electrode and thearc starter includes a spring. In some embodiments, the gas flowdiverter is anodized. In some embodiments, the gas flow diverterincludes a cap insert located substantially opposite the arcconstrictor, the cap insert substantially orienting the emissive memberand retaining the emissive member within the gas flow diverter. In someembodiments, a seal is disposed within the cap insert. In someembodiments, the consumable assembly includes a shield connected to thegas flow diverter. In some embodiments, the shield is connected to thegas flow diverter via a shield insulator.

In another aspect, the invention features a frame for a replaceable,unitary consumables cartridge configured for installation into a plasmaarc torch. The frame includes a hollow body adapted to receive atranslatable contact start electrode. The body has an internal surfaceand an external surface. The body includes a substantially cylindricalmetallic core. The body also includes an electrically insulativeovermolded plastic casing at least substantially surrounding acircumference of a distal end of the substantially cylindrical metalliccore. The body also includes a set of flow passages fluidly connectingthe external surface of the hollow body and the internal surface of thehollow body. The flow passages offset to impart a swirling fluid flowpattern to a plasma gases passing therethrough. In some embodiments, thesubstantially cylindrical metallic core is formed by stamping.

In some embodiments, the substantially cylindrical metallic core isformed by stamping. In some embodiments, the substantially cylindricalmetallic core is made of brass. In some embodiments, the substantiallycylindrical metallic core includes an anodized portion. In someembodiments, each flow passage in the set of flow passages is radiallyoffset from the other flow passages. In some embodiments, the flowpassages have a total cross-sectional area of about one square inch. Insome embodiments, a first end of the frame is configured to beinseparably connected to a nozzle such that the nozzle, frame, andelectrode are disposed as a single unit. In some embodiments, a firstend of the frame is configured to connect to a shield via a shieldinsulator, the shield thermally coupled to the frame.

In another aspect, the invention features a method of cooling a plasmaarc torch. The method includes providing a composite consumable having aframe defining a plurality of holes. The composite consumable hasintegrated components including an electrode, a nozzle and a shield. Theholes fluidly connect an external surface of the frame and an internalsurface of the frame. The holes are offset to impart a swirling fluidflow pattern to plasma gases passing therethrough. The method alsoincludes installing the composite consumable in the plasma arc torch.The method also includes flowing a cooling fluid through the pluralityof holes. The cooling fluid forms a fluid flow pattern that cools atleast one of the electrode, nozzle or shield, thereby removing at leastone watt of power from the plasma arc torch during operation. The frameis adapted to receive a translatable contact start electrode. The frameincludes (i) a substantially cylindrical metallic core; and/or (ii) anelectrically insulative overmolded plastic casing at least substantiallysurrounding a circumference of a distal end of the substantiallycylindrical metallic core.

In some embodiments, the substantially cylindrical metallic core isformed by stamping. In some embodiments, the substantially cylindricalmetallic core is made of brass. In some embodiments, the substantiallycylindrical metallic core includes an anodized portion. In someembodiments, each hole in the plurality of holes is radially offset fromthe other holes. In some embodiments, the holes have a totalcross-sectional area of about one square inch. In some embodiments, afirst end of the frame is configured to be inseparably connected to anozzle such that the nozzle, frame, and electrode are disposed as asingle unit. In some embodiments, a first end of the frame is configuredto connect to a nozzle and/or a shield via a shield insulator, theshield thermally coupled to the frame. In some embodiments, the set offlow passages extends into a further component inseparably attached to afront of the nozzle. In some embodiments, the substantially cylindricalmetallic core provides geometric stability, preventing the frame fromchanging shape, which could cause the electrode to cease and not slide,and/or cause the nozzle to fall off.

In another aspect, the invention features a method of manufacturing areplaceable, unitary consumables cartridge configured for installationinto a plasma arc torch. The method includes providing a hollow bodyadapted to receive a translatable contact start electrode. The body hasan internal surface and an external surface. The body includes asubstantially cylindrical metallic core. The method includes overmoldingan electrically insulative plastic casing on the hollow body. Theelectrically insulative plastic casing at least substantially surroundsa circumference of a distal end of the substantially cylindricalmetallic core. The method also includes providing a set of flow passagesfluidly connecting the external surface of the hollow body and theinternal surface of the hollow body. The flow passages are offset toimpart a swirling fluid flow pattern to a plasma gases passingtherethrough.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing discussion will be understood more readily from thefollowing detailed description of the invention when taken inconjunction with the accompanying drawings.

FIG. 1 is a cross-sectional schematic illustration of a cartridge for aplasma arc cutting system, according to an illustrative embodiment ofthe invention.

FIG. 2A is an isometric illustration of a unitary cartridge for a plasmaarc cutting system, according to an illustrative embodiment of theinvention.

FIG. 2B is a cross-sectional illustration of a unitary cartridge for aplasma arc cutting system, according to an illustrative embodiment ofthe invention.

FIG. 2C is a cross-sectional illustration of a unitary cartridge for aplasma arc cutting system, according to an illustrative embodiment ofthe invention.

FIG. 2D is a sectioned illustration of a plasma arc torch cartridgeframe having an overmolded plastic casing, according to an illustrativeembodiment of the invention.

FIG. 3A is an isometric illustration of an inner cartridge assembly fora plasma arc torch, according to an illustrative embodiment of theinvention.

FIG. 3B is a cross-sectional illustration of an inner cartridge assemblyfor a plasma arc torch, according to an illustrative embodiment of theinvention.

FIGS. 4A-4B are cross-sectional illustrations of consumable cartridgesfor a plasma arc cutting system, each cartridge having a nozzle, anelectrode, a swirl ring, a resilient element and an end cap, accordingto illustrative embodiments of the invention.

FIG. 5 is a cross-sectional illustration of a consumable cartridge for aplasma arc cutting system having a nozzle, an electrode, a swirl ring, aresilient element and an end cap, according to illustrative embodimentsof the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic illustration of a cartridge 100for a plasma arc cutting system, according to an illustrative embodimentof the invention. The cartridge 100 has a first end 104, a second end108, and a substantially hollow frame 112 having a first section 112Atoward the first end 104 and a second section 112B toward the second end108. The cartridge 100 also includes an arc emitter 120, an arcconstrictor 124, and a resilient element 128. The arc emitter 120 islocated within the frame 112 and is translatable relative to the frame112. As shown, the arc constrictor 124 forms a part of the frame 112(e.g., at the second end 108, but in some embodiments can be attached tothe frame 112). The resilient element 128 is in physical communicationwith the frame 112, e.g., is in direct physical communication with thefirst section 112A. In some embodiments, the resilient member 128 is acontact start spring element affixed to the arc emitter 120. Theresilient element 128 can be configured to pass a pilot current from theframe 112 to the arc emitter 120. The resilient element 128 can bias thearc emitter 120 toward one of the first end 104 or the second end 108 tofacilitate ignition at or near the arc emitter 120. The arc emitter 120can be an electrode and can include a highly emissive element 122 suchas a hafnium insert.

The first section 112A and second section 112B are joined at aninterface 132 to form a substantially hollow chamber. The interface 132provides a coupling force (F_(coupling)) that secures the first section112A and the second section 112B together. The resilient member 128 canimpart a separating force (F_(separating)) that biases the arc emitter120 toward at least one of the first section 112A or the second section112B. The separating force can have a magnitude that is less than amagnitude of the coupling force. In some embodiments, the coupling forceis provided at the interface 132 by at least one of a static frictionalforce, an adhesive force, or a normal force (e.g., a force countering adownward gravitational force) provided at a notch 136 of the interface132. In some embodiments, the coupling force is stronger than ispossible for a person to overcome by hand, either intentionally orinadvertently.

In some embodiments, the frame 112 includes at least one of a metal(e.g., aluminum) or other thermally conductive material. In someembodiments, the frame 112 is formed by molding. In some embodiments,the frame 112 is anodized (e.g., includes anodized aluminum, as setforth more fully below). In some embodiments, the frame 112 includes anelectrical insulator, for example anodized aluminum and/orthermoplastics (e.g., PEEK, Torlon, Vespel, etc.). In some embodiments,at least one of the first end 104 or the second end 108 of the frame 112includes a threaded region shaped to engage a complementary component.In some embodiments, the electrode 120 includes the resilient element128 such as a spring.

In some embodiments, an external surface of the cartridge 100 is shapedto connect to, or mate with, a retaining cap or a cartridge cap (notshown). In some embodiments, the retaining cap is replaceable, threaded,and/or snap-on. The cartridge cap can be disposed about (e.g., cansurround) the second end 108 of the frame 112. The cartridge cap can beshaped to contact the arc emitter 120 and to retain the arc emitter 120within the frame 112. The cartridge cap can define an aperture of thearc emitter 120. The cartridge cap can include a fluid sealing surfacedisposed about a circumference of the aperture of the arc emitter 120.In some embodiments, the cartridge cap substantially orients theelectrode 120 and retains the electrode 120 within the cartridge 100. Insome embodiments, the cartridge cap includes a seal.

The cartridge 100 can be a “consumable” cartridge or assembly ofconsumable components, e.g., the cartridge 100 can be replaced as a unitafter it reaches the end of its useful life. The cartridge 100 can be asealed unit that is not intended to have individual component partsreplaced. In some embodiments, individual components are irremovablydisposed within or integrated into the cartridge 100. For example, atleast a portion of the electrode 120 and the contact start springelement 128 can be irremovably disposed within the frame 112, e.g.,sealed within the frame 112 and/or not intended to be removed orreplaced by an operator. In some embodiments, the cartridge 100 is aconsumable component. In some embodiments, the components (e.g., frame112 and arc constrictor 124) may be connected via press fits or otherlike means with tight tolerances and will degrade, fracture, or fail ifseparated.

FIG. 2A is an isometric illustration of a unitary cartridge 200 for aplasma arc cutting system, according to an illustrative embodiment ofthe invention. Visible from the exterior are a plastic exterior section204, a metallic exterior section 208, and a copper exterior section 212(e.g., a nozzle shield). The plastic exterior section 204 and themetallic exterior section 208 are joined at a junction 206. In someembodiments, the junction 206 is included in or near a tapered region.In some embodiments, the plastic exterior section 204 is a retainingcap. In some embodiments, the metallic exterior section 208 is a shieldinsulator. In some embodiments, the metallic exterior section 208 isformed substantially of a material other than copper. In someembodiments, the copper exterior section 212 is formed of a pure orsubstantially pure copper or copper alloy. The components of thecartridge 200 are seen in more detail in FIG. 2B, described below.

FIG. 2B is a cross-sectional illustration of a unitary cartridge 200 fora plasma arc cutting system, according to an illustrative embodiment ofthe invention. In this view, additional elements of the cartridge 200are visible, including a nozzle body 216, a nozzle orifice 218, anelectrode 220 having an emitting element 222, an insulator sleeve 224having an elongated portion 224A, a resilient element 226, and anelectrode contact button 236 (e.g., made of brass). In the presentinvention, one or more of these elements can be redesigned to achieveone or more of the objectives set forth above.

For example, the nozzle body 216 can be formed from a conductivematerial (e.g., a highly conductive material such as aluminum) and canbe attached to (e.g., can be in direct physical contact with) otherparts of the cartridge 200. In some embodiments, the nozzle body 216 isin thermal communication with certain parts of the cartridge 200 (e.g.,via thermal conduction) but electrically isolated from other parts. Forexample, the nozzle body 216 can function as a heat sink for the nozzleorifice 218 while remaining electrically isolated from the nozzle shield212. Such a configuration can enhance cooling performance (for example,of the nozzle and the electrode) and reduce manufacturing costs bycomparison to previously used materials (e.g., as Vespel™). In someembodiments, the cartridge has a region with a thermal conductivity ofbetween about 200-400 Watts per meter per degree Kelvin (for example,aluminum may have a thermal conductivity of between 200-250 W/m-° K,while copper may have a thermal conductivity of between 350-400 W/m-°K). In some embodiments, the consumable cartridge has a heat capacity tocurrent ratio of 2-4 W/m-° K-A.

In addition, the nozzle body 216 includes a set of inlet swirl holes 228(e.g., swirl holes 228A and 228B). In some embodiments, the set of inletswirl holes 228 includes five swirl holes, or optionally between threeand ten swirl holes. The swirl holes 228 can be radially offset toimpart a swirl flow (e.g., radial and tangential velocity components) togases flowing therethrough (e.g., a shield gas, plasma gas, and/or aplenum gas). In this configuration, the nozzle body 216 provides theswirl function previously provided by a swirl ring, thus eliminating theneed for a traditional swirl ring. In addition, in some embodiments thenozzle body 216 is formed via a molding process, thus eliminating theneed for expensive and time-consuming drilling procedures to create theswirl holes. In some embodiments, the nozzle shield 212 includes anangle 232 that helps redirects fluid flow away from the plasma arcduring operation.

FIG. 2C is a cross-sectional illustration of a unitary cartridge 240 fora plasma arc cutting system, according to an illustrative embodiment ofthe invention. The unitary cartridge 240 can be similar in many respectsto the cartridge 200 shown in FIG. 2B but can differ in certain otherrespects. For example, the cartridge 240 utilizes a stamped torchinterface 250 (e.g., a stamped pieces of copper) having across-sectional “T”-shape. The interface 250 can allow the electrode toslide more freely than in the FIG. 2B configuration, which uses anelectrode with a nipple feature that forms a mating surface with thespring. In FIG. 2C, the cap and the nozzle body have been opened to easemanufacture and allow the electrode to slide freely into the nozzle bodyduring cartridge assembly. The spring can then rest on the electrode,and the stamped torch interface 250 can use a small tab feature 252 tosnap readily into the nozzle body, securing the electrode therein. Sucha configuration avoids the need to press fit multiple pieces together(and, in turn, avoids the need to have to achieve tight tolerancesbetween pieces) and/or the need to assemble different pieces of thetorch from different directions. Using the cartridge 240, a manufacturercan simply slide the electrode into place in one step.

In addition, the cartridge 240 uses a molded, slotted swirl feature 266to achieve the swirling function instead of using holes drilled in thenozzle body. In this configuration, during operation gas flows out ofthe slots 266 and into the plasma chamber to form the swirl gas aboutthe plasma arc. During operation, gas may also flow through molded gasshield channel 254, further cooling the nozzle body. Slots 266 form aset of swirl holes once the nozzle body, nozzle orifice, and/or nozzleliner are connected. Gas delivered to the slots is conveyed from thetorch through a chamber defined by an internal surface of the nozzlebody and an external surface of the nozzle liner (which, in combination,form the swirl holes). Such a configuration eliminates post-processmachining steps and the associated expenses. In addition, the cartridge240 includes a radial swage connection 258 between the nozzle orificeand the nozzle body. The radial swage connection 258 provides a robustconnection interface to allow contact to be maintained between thenozzle orifice and the nozzle body, but also exposes significant surfacearea for heat to be conducted from the nozzle orifice to the nozzlebody. Finally, in this embodiment, the electrode sleeve is removed andreplaced with a more traditional heat exchanger.

FIG. 2D is a sectioned illustration of a plasma arc torch cartridgeframe 280 having an overmolded plastic casing 282, according to anillustrative embodiment of the invention. The frame 280 includes ahollow body 284 adapted to receive a translatable contact startelectrode. The body 284 has an internal surface 286 and an externalsurface 288. The body 284 includes a substantially cylindrical metalliccore 290, which can be formed by stamping. The body 284 also includesthe electrically insulative overmolded plastic (such as a thermoset orthermoplastic) casing 282, which at least substantially surrounds acircumference of a distal end of the substantially cylindrical metalliccore 290. In some embodiments, the body 284 also includes a set of flowpassages 292 (e.g., at a distal end of the cartridge frame 280, asshown) fluidly connecting the external surface 288 and the internalsurface 286. The flow passages 292 can be offset to impart a swirlingfluid flow pattern to plasma gases passing therethrough. In oneembodiment, the holes impart a swirling flow to a plasma gas enteringinto the plasma chamber into the cartridge, a portion of the plasmamoving distally to generate a plasma arc and a portion of the gas movingproximally to cool the electrode. The flow passages 292 can be formedentirely within the plastic, e.g., by molding, and can enable crimpingwith another cartridge or torch component, e.g., the proximal end of anozzle or shield (not shown). The crimped component can form part of theswirling flow passages 292.

In some embodiments, the cylindrical metallic core 290 helps to overcomecertain thermal cycling and overheating issues with using moldedplastics in a swirl ring. For example, plastics used in this context canexhibit a localized melting of the inner diameter, e.g., when theelectrode is close to end of its life. At this point the electrodetemperature can be higher than the melting point of the plastic used,causing it to melt and deform. Under these circumstances, the electrodein turn can be prevented from moving freely inside the swirl ring. Inextreme cases, this malfunction can damage the torch (when the arc canbe started but the electrode cannot move). In other failure modes, thenozzle may separate from the frame. As a solution, thermal plastic canbe overmolded on a stamped brass piece to provide geometric stabilitysuch that the aforementioned melting and warping does not occur. Thesleeve material can be a metal alloy and can be used with or without asecond metal coating. In some embodiments, brass is used. Other metalsthat can be used include nickel-plated brass, copper, aluminum, steel,or other metals. Another benefit of overmolded plastic on a brass sleevecan be a decreased cost (e.g., $1.30 as compared with about $5 forVespel). Such embodiments can reduce or eliminate local melting in theinner diameter and can provide a reliable starting performance androbust torch.

FIG. 3A is an isometric illustration of an inner cartridge assembly 300for a plasma arc torch, according to an illustrative embodiment of theinvention. Visible from the exterior are a shield 304 having vent holes306 (e.g., holes 306A-D as shown), a nozzle body 308 having flow holesor inlet swirl holes 312 (e.g., holes 312A, 312B as shown in FIG. 3A), afront insulator (or shield insulator) 314, and a rear insulator (or lockring) 316. These and additional elements are described more fully inconjunction with the cross-sectional view shown in FIG. 3B below.

FIG. 3B is a cross-sectional illustration of the inner cartridgeassembly 300 of FIG. 3A, according to an illustrative embodiment of theinvention. In this view, several additional components of the innercartridge assembly 300 are visible, including an electrode 320 having anemitting element 322, an arc constrictor or nozzle orifice 324, shieldflow holes 328 (e.g., flow holes 328A-B as shown) directed toward thenozzle orifice 324, an insulator sleeve 332, and a cooling gas flowchannel 336. In this embodiment, the nozzle body 308 functions as thecartridge frame to which other parts attach.

A number of features of the inner cartridge assembly 300 can enhance itscooling capabilities. First, the nozzle body 308 can be made ofaluminum, which can enhance heat conduction over previous materials andconfigurations as described above. Second, the nozzle orifice 324 can bemade of copper and can be pressed onto the nozzle body 308. In suchembodiments, the nozzle body 308 can serve as a heat sink for the coppernozzle orifice 324. Third, improved gas flow surfaces, can assist incooling, e.g., with shield gas flowing forward through holes 328A, 328Bjust outside of the press area. A press fit arrangement can also provideimproved thermal conduction paths between torch parts as a result oftight tolerances between the surfaces of the parts. In some embodiments,the press fit arrangement includes an interference fit and/or a tabbedor interlocking fit having one or more step-like features. In addition,the small size of the press fit design has the additional advantages ofreducing manufacturing and/or material costs and simplifying manufactureand assembly of the components (e.g., by having fewer parts).

The nozzle shield 304 can also be made of copper and can be pressed ontoan anodized aluminum insulator 314 at a surface 305A. This assembly canthen be pressed onto the nozzle body 308 at a press fit surface 305B. Insuch embodiments, the shield insulator 314 connects the nozzle body 308to the shield 304. In some embodiments, the shield insulator 314 ispress fit to the nozzle body 308. In some embodiments, the shieldinsulator 314 is an electrically insulative ring and/or includes a setof press-fit surfaces 305A, 305B that connect the shield 304 and thenozzle body 308. The shield insulator 314 can connect the nozzle body308 to the shield 304 such that the nozzle body 308 and the shield 304are electrically insulated from one another while still transferringthermal energy to one another. In some embodiments, using a two-pieceshield insulator can increase (e.g., double) electrical insulationabilities as a result of increasing contact surfaces.

The nozzle shield 304 can be considerably smaller than previous shields,allowing for efficient manufacture and assembly of components, improveddurability, and greater assurances of proper orientation of cartridgeparts relative to one another. By way of example, for a 45-amp system, aprior art stock shield might have a diameter of about one inch and amass of about 0.04 pounds, whereas a cartridge shield in accordance withthe current invention can have a diameter of about 0.5 inches with amass of less than 0.01 pounds (e.g., about 0.007 pounds). For a 105-ampsystem, a prior art stock shield might have a diameter of about one inchwith a mass of about 0.05 pounds, whereas a cartridge shield inaccordance with the current invention can have a diameter of about ahalf inch with a mass of about 0.01 pounds (e.g., 0.013 pounds).

The smaller size configuration can carry significant advantages. First,components having a reduced mass have a reduced heat capacity, whichallows the components to be rapidly cooled during post-flow and/orallows more heat to be transferred to the cooling gas during operation.Second, a smaller shield can attain comparatively higher temperaturesduring operation and can transfer more heat to the cooling gas. In someembodiments, the nozzle shield 304 is exposed to a cold gas entering theshield area, e.g., via shield flow holes 328, which can further reducethe temperature. The flow holes 328 can each have a total crosssectional area of at least about one square inch.

In some embodiments, the electrode 320 includes a base made of copper.In some embodiments, the electrode 320 base has a small diameter with apressed-on insulator sleeve 332 made of anodized aluminum and/or plasticused for electrical isolation. In some embodiments, a cooling gas flowchannel or gap 336 exists between the insulator sleeve 332 and thenozzle body 308. In some embodiments, a cool gas flows in the gap 336.In some embodiments, a “dumbbell” configuration 340 defined by two endcontacts 340A, 340B is used, which can reduce or minimize contact areabetween the nozzle body 308 and the insulator sleeve 332. Such aconfiguration can reduce friction between parts.

In some embodiments, the sleeve 332 contacts the electrode 320, whichcan be part of a separate current path from the nozzle body 308 and/or adifferent portion of the current path from the nozzle body 308. In someembodiments, the electrode 320 and the nozzle body 308 can beelectrically separated by a gap to create the arc and/or to ensureproper orientation of the parts in the torch. In such embodiments, thenozzle 308 and the electrode 320 can be in physical contact between thesleeve 332 and the nozzle body 308. In such embodiments, insulativelayers are needed in this region so that current is able to pass throughthe emitting element 322.

In some embodiments, a wall of the nozzle body 342 near which theelectrode 320 moves can stay comparatively cool during operation as gasflow passes both on the inside of the nozzle body 308 and directlyacross an exterior surface 344 of the nozzle 324. The material choice(e.g., aluminum or another metal) for the nozzle body 342 designprovides for a better conduction path and heat sink ability as comparedwith previous materials such as Vespel™. Such factors assist in coolingthe electrode isolation piece and allow the electrode to function evenafter a deep pit is formed in the emitting element from electrode use.

In some embodiments, a lock ring 316 (or isolation ring) forms aninterface 346 between the cartridge 300 and the torch. In someembodiments, the lock ring 316 can be made of anodized aluminum. Thelock ring 316 can be pressed into the nozzle body to “trap” the moveableelectrode 320. The lock ring 316 can contain the components within thecartridge 300 and electrically isolate the torch. In some embodiments,the lock ring 316 is replaced by heat shrinking or gluing. In someembodiments, the lock ring 316 is shaped to orient the cartridge 300(e.g., axially), to optimize gas flow, to enable electrical connectionto the cathode, and/or to provide electrical isolation.

In various embodiments described herein, the cartridges or consumableassemblies are about 3.5 inches in length and 1.1 inches in diameter. Insome embodiments, the retaining cap is considered part of the torch,e.g., not a consumable component. In such configurations, machiningsteps can be minimized, with no machining necessary after assembly (ascompared to some torch assemblies that require a final machining step toachieve functional axiality of the cartridge). In some embodiments, thereduction in swirl holes can minimize drilling operations compared toprior art swirl rings. In some embodiments, replacing Vespel™ withaluminum can significantly reduce manufacturing costs of the cartridge.In some embodiments, copper is used only in certain locations in theelectrode, nozzle, and/or orifice, which can reduce manufacturing costsby reducing the use of this expensive material. For example, copper canbe concentrated primarily in an inner core or region. While copper canbe desirable for its thermal and electrical properties, it is also moreexpensive than other materials, and so designs that minimize its usageare sought.

FIGS. 4A-4B and 5 are cross-sectional illustrations of consumablecartridges for a plasma arc cutting system, each cartridge having anozzle, an electrode, a swirl ring, a resilient element and an end cap,according to illustrative embodiments of the invention. FIG. 4A shows anexemplary cartridge design 400. As shown, the cartridge 400 includes aswirl ring 402, an end cap 406, a nozzle 408 and an electrode 404. Theelectrode 404 can be a spring-forward electrode for a contact startplasma arc torch, where a resilient element 412 (e.g., a spring) exertsa separating force on the distal end of the electrode 404 to bias theelectrode 404 away from the end cap 406 and toward the nozzle 408. Theresilient element 412 can also be a part of the cartridge 400. Thecartridge 400 can include a starting mechanism for contact starting aplasma arc torch upon assembly into the torch.

The swirl ring 402 can extend substantially over the length of theelectrode 404 along a longitudinal axis 410 of the electrode 404. Insome embodiments, the swirl ring 402 is manufactured through injectionmolding of high-temperature thermoplastics (e.g., PAI, PEI, PTFE, PEEK,PEKPEKK, etc). Use of thermoplastics to manufacture swirl rings canreduce cartridge cost in comparison to Vespel™, which is a material thathas been used to manufacture swirl rings, but is comparatively moreexpensive. It is known that thermoplastics have operating temperaturesthat are lower than Vespel™ (a thermoset), which can impact theintegrity of swirl rings and electrode life. However, the cartridgedesigns of the present technology, which can incorporate swirl ringsmade from thermoplastics resins having various fortifying additives thatprovide the desired thermal resistance and/or thermal conductivity(e.g., glass fibers, minerals, boron nitride (BN), and/or Cubic BN),have resolved the high temperature performance issues, thus enabling theeffective use of thermoplastics in these cartridges. This is achievedsince (1) thermoplastics have a sufficiently high-temperature resistanceand (2) a cartridge design that properly incorporates thermoplastics canavoid exposure of the thermoplastics to excessive temperatures duringoperation. In addition, when an electrode experiences an end-of-lifeevent, which is also the end of life of the cartridge, the simultaneousmelting of the plastic material is not problematic.

The end cap 406 can be made of a conductive material, such as copper.The end cap 406 can be inexpensively formed via stamping from a materialblank and can be irremovably inserted, press fit or over molded onto thecartridge 400. The end cap 406 is configured to contain the resilientelement 412 within the cartridge 400 and compress the resilient element412 against the distal end of the electrode 404 such that the resilientelement 412 exerts a separating force on the distal end of the electrode404 to bias the electrode 404 toward the nozzle 408. In someembodiments, end cap 406 may be shaped to matingly engage a patternedtorch head and/or may include a set of fluid flow holes formedtherethrough.

In some embodiments, an unreleasable snap-fit interface 414 is formedbetween the swirl ring 402 and the nozzle 408 to join the two consumablecomponents together as a part of the cartridge 400. In addition, asecond snap-fit interface 416 can be formed between the swirl ring 402and the end cap 406 to join the two consumable components together as apart of the cartridge 400. Other manufacturing and assembly options areavailable and viable. For example, the swirl ring 402 can be over-moldedonto the end cap 406. The end cap 406 can also be capsulated by theswirl ring 402 and the resilient element 412 (e.g., a spring), where theend cap 406 can move within the cartridge 400.

FIG. 4B shows another exemplary cartridge design 450. As shown, thecartridge 450 includes a swirl ring 452, an end cap 456, a nozzle 458and an electrode 454. In some embodiments, the cartridge 450 alsoincludes a resilient element 462 that functions similarly as theresilient element 412 of FIG. 4A. The cartridges of FIGS. 4A and 4B havedifferent electrodes (e.g., different sizes of heat exchanger flanges,circumferential flange for uniform flow), different nozzles (e.g.,different swirl ring attachment), and different swirl rings (e.g.,different swirl holes and attachment). In the cartridge design 450 ofFIG. 4B, an interface 464 is formed as the swirl ring 452 is insertedinto position in relation to the nozzle 458. Another interface 466 canbe formed between the swirl ring 452 and the end cap 456.

FIG. 5 shows another exemplary cartridge design 500. As shown, thecartridge 500 includes a swirl ring 502, a sleeve 514, an end cap 506, anozzle 508 and an electrode 504. In some embodiments, the cartridge 500also includes a resilient element 512 that functions similarly as theresilient element 512 of FIG. 4A. The sleeve 514 and/or end cap 506 canbe made from a conductive material (e.g., copper) using a stampingmethod. The sleeve 514 can be press fit or over molded onto thecartridge 500. The end cap 506 can be a part of the sleeve 514.Therefore, the sleeve 514 and the end cap 506 can be constructed as asingle component piece.

As shown, the swirl ring 502 can be relatively short in comparison tothe swirl ring 402 such that the swirl ring 502 only extends along aportion of the length of the electrode 504 in the longitudinal axis 510.Similar to the swirl ring 402, the swirl ring 502 can be manufacturedthrough injection molding of high-temperature thermoplastics (e.g.,Torlon™). A snap-fit interface 520 can be formed between the swirl ring502 and the nozzle 508 to join the two consumable components together asa part of the cartridge 500. Another snap-fit interface 518 can beformed between the swirl ring 502 and the sleeve 514 to join the twoconsumable components together as a part of the cartridge 500.Alternatively, the swirl ring 502 can be over-molded onto the sleeve514.

There are many benefits associated with using a cartridge in a plasmaarc torch. First, such a design promotes ease of use through quickchange capabilities, short setup time and ease of consumable selectionfor an end user. It also provides consistent cut performance because asuite of consumables are changed at once when the cartridge is changed.In contrast, variation in performance is introduced when components arechanged individually at different times. For example, long term re-useof the same swirl ring can cause dimensional alteration after eachblow-out, thereby altering the performance quality even if all othercomponents are changed regularly. In addition, since the manufacturingand/or installation cost of a cartridge is lower than the combined costof a set of consumables, there is a lower cost associated with percartridge change than per change of a set of consumables. Furthermore,different cartridges can be designed to optimize torch operation withrespect to different applications, such as marking, cutting, maintaininglong life, etc.

While the invention has been particularly shown and described withreference to specific preferred embodiments, it should be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit and scope of theinvention as defined by the following claims.

What is claimed is:
 1. A frame for a replaceable, unitary consumablescartridge configured for installation into a plasma arc torch, the framecomprising: a hollow body adapted to receive a translatable contactstart electrode, the body having an internal surface and an externalsurface, the body including: a substantially cylindrical metallic core;an electrically insulative overmolded plastic casing at leastsubstantially surrounding a circumference of a distal end of thesubstantially cylindrical metallic core, and a set of flow passagesfluidly connecting the external surface of the hollow body and theinternal surface of the hollow body, the flow passages offset to imparta swirling fluid flow pattern to a plasma gases passing therethrough. 2.The frame of claim 1 wherein the substantially cylindrical metallic coreis formed by stamping.
 3. The frame of claim 1 wherein the substantiallycylindrical metallic core is made of brass.
 4. The frame of claim 1wherein the substantially cylindrical metallic core includes an anodizedportion.
 5. The frame of claim 1 wherein each flow passage in the set offlow passages is radially offset from the other flow passages.
 6. Theframe of claim 1 wherein the flow passages have a total cross-sectionalarea of about one square inch.
 7. The frame of claim 1 wherein a firstend of the frame is configured to connect to a nozzle.
 8. The frame ofclaim 7 wherein the set of flow passages extends into a furthercomponent inseparably attached to a front of the nozzle.
 9. A method ofcooling a plasma arc torch, the method comprising: providing a compositeconsumable having a frame defining a plurality of holes, the compositeconsumable having integrated components including an electrode, a nozzleand a shield, the holes fluidly connecting an external surface of theframe and an internal surface of the frame, the holes offset to impart aswirling fluid flow pattern to plasma gases passing therethrough;installing the composite consumable in the plasma arc torch; and flowinga cooling fluid through the plurality of holes, the cooling fluidforming a fluid flow pattern that cools at least one of the electrode,nozzle or shield, wherein the frame is adapted to receive a translatablecontact start electrode and includes (i) a substantially cylindricalmetallic core; and (ii) an electrically insulative overmolded plasticcasing at least substantially surrounding a circumference of a distalend of the substantially cylindrical metallic core.
 10. The method ofclaim 9 wherein the substantially cylindrical metallic core is formed bystamping.
 11. The method of claim 9 wherein the substantiallycylindrical metallic core is made of brass.
 12. The method of claim 9wherein the substantially cylindrical metallic core includes an anodizedportion.
 13. The method of claim 9 wherein each hole in the plurality ofholes is radially offset from the other holes.
 14. The method of claim 9wherein the holes have a total cross-sectional area of about one squareinch.
 15. The method of claim 9 wherein a first end of the frame isconfigured to connect to a shield via a shield insulator, the shieldthermally coupled to the frame.
 16. A method of manufacturing areplaceable, unitary consumables cartridge configured for installationinto a plasma arc torch, the method comprising: providing a hollow bodyadapted to receive a translatable contact start electrode, the bodyhaving an internal surface and an external surface, the body including asubstantially cylindrical metallic core; overmolding an electricallyinsulative plastic casing on the hollow body, the electricallyinsulative plastic casing at least substantially surrounding acircumference of a distal end of the substantially cylindrical metalliccore, and providing a set of flow passages fluidly connecting theexternal surface of the hollow body and the internal surface of thehollow body, the flow passages offset to impart a swirling fluid flowpattern to a plasma gases passing therethrough.